Earthquakes and Floods - Orchids The International School
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Natural Disasters

Concept: Earthquakes and Floods

What are natural disasters?

  • Any natural event or phenomenon which may lead to the destruction of life and property is called a natural disaster.
  • Examples:

    Earthquakes, volcanoes, tsunamis, etc.

  • A natural disaster may be triggered due to natural processes like tectonic plate movement or certain man-made causes like mining, deforestation, etc.
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Major causes of natural disasters:

  1. Deforestation:
    • One of the major causes of natural disasters like floods and landslides is deforestation.
    • The roots of trees are capable of absorbing excess water from the water bodies, which prevents the occurrence of floods.
    • Plant roots also have a firm grip on the soil and do not allow it to slide during heavy rainfall, thereby preventing landslides to a large extent.
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  2. Mining:
    • Mining involves the extraction of valuable minerals like coal, diamond, gold, aluminium, etc., from the earth.
    • Underground mining is accompanied by a series of explosions that often lead to tremors resulting in earthquakes.
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  3. Tectonic plate movements:
    • The lithosphere is made of tectonic plates, and the movement of these plates millions of years ago led to the formation of continents.
    • These tectonic plates, when moving vigorously, lead to natural disasters like earthquakes and tsunamis that cause vast destruction of life and property.

Some natural disasters and their effects are described below—

Earthquakes:

  • The sudden shaking of the earth's surface due to the effect of seismic waves is called an earthquake.
  • The point from where the seismic waves originate is called the focus.
  • These waves travel to the surface of the earth, and the point where they touch the surface of the earth is called the epicentre.
  • The areas near the epicentre are most affected, and the intensity of the impact reduces as one moves away from the epicentre.
  • The study of earthquakes is called seismology.
  • The intensity of an earthquake can be measured using the Ritcher Scale.
  • The seismic waves that cause earthquakes can be studied using a seismograph.
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  1. Preparedness during an earthquake:
    • An earthquake can be moderate or intense depending upon the distance of the focus from the epicentre.
    • However, one should take care of certain things when an earthquake is felt.
    • The following things should be done during the occurrence of an earthquake—
      • Getting out of the house/building and moving to open grounds.
      • If someone is indoors, they should try to find a solid table and get under it, as that will prevent heavy things from falling on the person.
      • Avoid touching electrical appliances and switches during an earthquake, as turning them on or off may lead to electric shocks.
      • Stay away from heavy objects like book racks, wardrobes, cupboards, etc., as they may fall due to tremors.
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  2. Effects of earthquakes:
    • Earthquakes that are intense often lead to the destruction of life and property.
    • Much time and effort are required to bring life to normal again.
    • Different government and non-government organisations help in the process of rehabilitation.
    • Temporary settlements are done for the people to live until the repairing work takes place.
    • Basic necessities like food, water, medicine and clothes are provided to the people affected by the calamity.
  3. Some massive earthquakes in India:
  4. S.no. Date Place
    i) 26th January 2001 Kutch, Gujarat
    ii) 30th September 1993 Latur, Maharashtra
    iii) 20th October 1991 Uttarkashi, Uttarakhand
    iv) 15th August 1950 Assam
  5. Earthquake zones of India:
  6. The states in India are divided into different earthquake zones based on the probability and frequency of earthquakes. The different zones are as follows—

    • Zone 1 and 2: These zones are at a minimum risk of earthquakes. Places like Vizag, Ajmer, Allahabad, Bhilai, Ranchi, Udaipur, Jaipur, etc., lie in these zones.
    • Zone 3: In this zone, moderate earthquakes can occur. Himalayan plains (western), Tamil Nadu, Karnataka Uttar Pradesh and some regions of Andaman Nicobar islands lie in this zone. Other places which fall under this category are Vellore, Goa, Nasik, Mumbai, and Thiruvananthpuram.
    • Zone 4: It is also called the high-risk damage zone. The following places/states lie in this zone—Uttarakhand, Moradabad and Gorakhpur in Uttar Pradesh, Darjeeling in West Bengal, Gangtok in Sikkim and Shimla in Himachal Pradesh.
    • Zone 5:The areas located in this zone are highly prone to earthquakes like Bhuj in Gujarat, Guwahati in Assam, Darbhanga in Bihar and Srinagar in Jammu and Kashmir.

Floods:

  • When a large amount of water accumulates on the dry areas of land due to overflowing water bodies or heavy rainfall, it is called a flood.
  1. Cause of floods:
      Floods occur due to the following reasons—
      • Heavy rainfall
      • Destruction of dams
      • Overflowing of water bodies
      • Tsunamis that may cause floods in the coastal areas.
  2. Preparedness during floods:
    • Listening to the warnings and weather forecasting reports on radio or television.
    • Making a first aid kit with some essential medicines and ointments.
    • Collecting dry food and fresh drinking water as much as possible.
    • Trying to cover the hands and feet with rubber gloves and boots.
    • Getting batteries, a torch and a phone charger.
  3. Effects of floods:
    • Loss of life:The forceful uncontrollable entry of water leads to the death of people as they are exposed to several injuries or get drowned in the water, or may flow away to other places due to the strong water currents.
    • Loss of property:The massive flow of water destroys buildings, houses and other buildings.
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    • Outbreak of diseases:Flood water carries a lot of germs. These germs cause water-borne diseases like typhoid and diarrhoea.
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    • Unavailability of fresh water and food:Due to flooding, fresh water and food are not available, which worsens the situation.
  4. What should one do after floods?
    • Stay away from the floodwater as far as possible, because it can make you sick.
    • Keep yourself protected from sharp objects or any injury as lack of medical facilities during a flood may pose difficulty in treatment.
    • Ensure that you drink clean water and food.
    • Follow the warnings and guidelines declared by the government regarding evacuation.

New Words

Evacuating: Moving from a place of danger to a safer place.

Preparedness: A state of being ready for any situation.

Ointments: Medications for external use, especially for the skin.

Landslide: A form of natural disaster accompanied by sliding a part of rock or surface of the earth on a slope.

Lithosphere: It is the hard solid outer part of the earth.


Did You Know?

  • Earthquakes can give rise to gigantic waves in the oceans that are called tsunamis.
  • Some mild shocks occur before the actual earthquake, called foreshocks.
  • The largest earthquake recorded to date is the one that occurred in Chile in 1960, which had a magnitude of 9.6 on the Ritcher scale.
  • Flash floods can raise the water level to a height of 10-20 feet.
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